This paper focuses on the transformation of the philosophical views of Gottlob Benjamin Jäsche (1762--1842), professor of theoretical and practical philosophy at Tartu University (1802--1838). In the history of philosophy, Jäsche is known as a compiler and publisher of Immanuel Kant's handbook of lectures on logic (1800). His critique of Spinozism and pantheism is also noteworthy (Der Pantheismus nach seinen verschiedenen Hauptformen I-III, 1826--1832). Jäsche was characterised as a rather strict, even orthodox disciple of Kant's philosophy. However, it was noticed that his Kantianism was influenced by the philosophy of Friedrich Heinrich Jacobi. This paper mainly examines the meaning of Jacobi's philosophical doctrine of belief or faith (Glaube), including the meaning of the criticism of Spinozism and pantheism during the turn in Jäsche's philosophy at the end of the first decade of the 19th century. The analysis focuses on one of Jäsche's manuscript works, entitled Liebe und Glaube (Love and Faith). This is a peculiar spiritual diary, the writing of which was induced by the death of Jäsche's wife, Sally in February 1808. In his diary Jäsche tries to explicate the tragedy and through it to overcome the spiritual as well as philosophical crisis that assailed him as a consequence of his wife's untimely death. The fact that Kant's philosophy did not help Jäsche cope with his wife's death became decisive, because through Kantianism he was unable to find a philosophical explication of the supernatural experience that he had lived through. Jäsche emerges from the bind thanks to Jacobi's philosophy of belief. Although, broadly speaking, Jäsche remained within in the framework of Kant's philosophy, this was not merely a matter of making small adjustments and shifting emphases, but rather entailed a thorough reconsideration of central notions of Kant's philosophy.